Opposition MPs and Tory rebels ensured the bill to prevent Britain leaving the EU without a deal in ace passed its first stage of reading by 329 votes to 300.

British Prime Minister Boris Johnson on Wednesday suffered another parliamentary blow over Brexit as MPs have backed a bill to block a no-deal Brexit, which could trigger a snap general election next month.

Opposition MPs and Tory rebels ensured the bill to prevent Britain leaving the EU without a deal in ace passed its first stage of reading by 329 votes to 300.

If it is passed in full later on Wednesday, it will force Johnson to ask for the EU for extension to the October 31 Brexit deadline if a so-called divorce pact is not in place by mid-October. Johnson has already warned that he would rather push for an immediate vote on an early general election for October 15 if the "surrender bill" cleared all the Commons stages.

The vote that he lost was on the second reading - the parliamentary stage which examines the main principles of the bill - and was the first chance for MPs to show whether they supported the bill.

MPs are now debating amendments to the bill - put forward by MPs but chosen by the Speaker - ahead of another vote on Wednesday.

It would be after this that the UK PM might carry out his threat of tabling his motion for an election.

Johnson suffered a humiliating defeat in Parliament on Tuesday when he lost his wafer thin majority and rebel Conservatives joined opposition MPs in voting against a no-deal departure.